Butterfly valve with shim seat adjustment

ABSTRACT

A butterfly valve is provided which includes a resilient ring defining a valve disc seat and chocks and shims arranged so as to compress the ring and expand it radially.

United States Patent 1 1 1 3,726,505 Williams Apr. 10, 1973 [s41BUTTERFLY VALVE WITH SHIM SEAT [56] References Cited ADJUS H'IENT UNITEDSTATES PATENTS [75] Inventor: Hubert L. Williams, Hinsdale, Ill.

3,630,485 12/1971 -Williams ..251 307 [73] Assignee: Clow Corporation,Oak Brook, Ill.

Primary Examiner-Henry T. Klinksiek [22] 1971 Attomey-Fitch, Even, Tabin& Luedeka [21] Appl.No.: 198,718

57 ABSTRACT 52 US. Cl .Q .251/307 277/188 A butterfly valve is Pmvidedwhich includes siliem 51 Int. Cl. ..F16k 1/226 F ISj 15/16 ring defininga valve Seat and Shims [58] Field of Search ..251/170, 171, 172,arranged as to the ring and expand it radially.

1 0 Claim, 5 Drawing Figures PATENTEDAPR 1 0191s sum 1 BF 2 [1v VENTORHuaser A. Wan/ms BUTTERFLY VALVE WITH SHIM SEAT ADJUSTMENT The presentinvention relates to butterfly valves and, more particularly,tobutterfly valves which include a resilient valve seat adapted tocooperate with the periphery of the valve disc to provide a seal.

Butterfly valves conventionally include a valve body defining a fluidflow passageway, and a circular or generally circular valve disc mountedwithin the valve body for pivotal movement between an open positionparallel to the longitudinal axis of the flow passageway and a closedposition generally perpendicular to the longitudinal axis of the flowpassageway. When in the closed position a peripheral portion of the discengages a seat defined by the valve body to provide a fluid-tight seal.One of the interengaging sealing surfaces is preferably defined by aresilient material to assure a tight fit between these surfaces. Inaddition, the position of one of the surfaces is desirably renderedadjustable to eliminate the necessity of precise machining when thevalve is fabricated and to permit compensation for wear and otherfactors adverse to a fluid-tight seal after the valve has been placed inservice.

One approach for achieving the desired surface adjustment is to providemeans for placing the resilient material defining one of theinterengaging sealing surfaces in compression so as to expand thematerial and thereby shift the position of that sealing surface. Thepresent invention relates to such a means particularly adapted toplacing in compression and expanding a resilient material which definesthat sealing surface which is supported by the valve body and isengageable by the valve disc. I

Accordingly, it is the principal object of the present invention toprovide an improved butterfly valve of the type which includes a valvedisc seat defined by a resilient material and means for placing theresilient material in compression so as to shift the position of the tothat of FIG. 2 but showing an alternate embodiment of'the invention;

FIG. 4 is a plan view of a portion of the butterfly valve constructionshown in FIG. 3; and

FIG. 5 is a fragmentary plan view showing another embodiment of theinvention.

Referring more specifically to the drawings, there is illustrated inFIG. I a butterfly valve which incorporates various of the features ofthe invention. The valve 10 includes a valve body 12, only a portion ofwhich is illustrated. Basically, the valve body includes a generallycylindrical wall 14 defining a fluid flow passageway 16, thelongitudinal axis of this passageway being hereinafter referred to asthe flow axis of the passageway. Although not shown in the drawing, itis contemplated that means be provided at each end of the cylindricalwall 14 to facilitate attachment of the valve body to suitable segmentsof pipe or conduit.

Projecting from the valve body at diametrically opposed locations are apair of trunnions 18 which define suitable journals fora valve stem 20.Although all of the internal details of construction of the trunnionsare not shown, each journal is illustrated as being lined with asuitable bearing material indicated at 22, and each may be provided witha sealing element such as an O-ring 24 disposed in a suitable groove, asshown, or in the bearing space. One end 26 of the valve stem 20 projectsoutwardly of its trunnion 18 for connection to a suitable operatingdevice (not shown) by means of which rotation of the stem is effected.

A valve disc 28 is mounted on the valve stem and, as illustrated, iscylindrical and includes a diametrical bore to receive the valve stem20. However, the disc may be provided with diametrically opposed flatsunder some circumstances at the points where the valve stem is joined tothe disc. Suitable holes extend through the disc and stem to receivepins 30 by means of which the disc is secured to the stem, but the discmay also be keyed or otherwise held to the stem. The disc includesadjacent one face a radially projecting peripheral flange 32 machined toprovide an edge 34 which is the only portion of the disc to engage thevalve seat 36 (FIGS. 2 and 3), soon to be described. The plane withinwhich the edge 34 of the valve disc lies is offset from the axis ofrotation of the disc, as defined by the longitudinal axis of the valvestem 20, to make possible 360 contact between the edge 34 and the valveseat 36.

In order to accommodate the means defining the valve seat 36, the valvebody 12 is provided with an inner annular groove 38 in the surface ofthe cylindrical wall 14 which defines the fluid flow passageway 16. Thegroove is positioned so as to be intersected by the plane defined by thevalve disc edge 34 when the disc is in the closed position transverse tothe fluid flow passageway and includes a base 40 and opposed side walls42 and 44 (FIGS. 2 and 3). The base 40 may define a generallycylindrical surface, and is so illustrated, while the side walls 42 and44 are contoured (FIGS. 2 and 3). More specifically, the groove wall 42nearest the valve stem 20, hereinafter sometimes referred to as the leftwall because of its location in the drawings, is undercut to provide aslot 46 relative to which an upper portion 48 is disposed in overhangingrelation. The face of the upper portion 48 is slightly inclined relativeto the flow axis of the passageway 16. The opposite or right wall 44 ofthe groove is provided with a projection 50 adjacent its upper edgewhich overhangs the groove base 40, and the face 51 of the projection isalso inclined relative to the flow axis of the passageway toward thebase 40 and may be roughly parallel to the inclined face of the upperportion 48 of the opposite groove wall 42. The face 51 of the projection50 defines a bearing surface, the function of which will become apparentshortly.

The valve seat 36 is defined by the radially inner surface of a ring 52formed of a resilient elastomeric material such as rubber which willexpand under compression if otherwise unrestrained. Various materialsknown in the art for this particular application are suitable. The ring52 may be formed of one piece or two or more pieces, which pieces may ormay not be connected or bonded to one another at their adjacent ends. Itis formed to provide a pair of axially extending flanges 54 and 56adjacent its outer periphery (FIGS. 2 and 3), and extends radially fromthese flanges a distance greater than the depth of the groove 38 so thatthe seat 36, defined by the inner surface of the ring 52, is disposedinwardly of the inner surface of the valve body walls defining the fluidflow passageway 16. As shown, the ring is of a lesser axial width thanthe groove 38, i.e., the axial width of the ring at its outer surfacedefined by the flanges 54 and 56 is less than the axial width of thebase 40 of the groove. However, the flanges 54 and 56 could extend fromthe wall 44 to the wall 46 of the groove if desired. The seat 36 itselfmay define a cylindrical surface but, as shown in FIG. 2, is inclinedslightly relative to the flow axis and therefore defines a conicalsurface to enhance the sealing ability of the valve. In the embodimentof FIG. 3, the seat 36' is curved and defines a convex surface toaccomplish the same function. The leading and trailing edges of the ringshown in FIG. 2 are chamferred adjacent the seat 36, as at 58.

As disposed in the groove 38, the outer surface of the ring 52 rests onthe base 40 of the groove, with the flange 54 of the ring disposedwithin the slot 46 of the groove wall 42, thereby serving topartially-lock the ring within the groove. Preferably, the groove wall42 and the adjacent surface of the ring 52 are so shaped as to permitintimate engagement between the wall and ring. In the embodimentillustrated in FIG. 2, the edges of the groove wall and the flange 54 ofthe ring are each rounded to eliminate stress concentrations. Because ofthe difference between the axial width of the ring and the axial widthof the groove, an annular space is provided between the opposite surfaceof the ring (i.e., the surface on the right in FIGS. 2 and'3) and thewall 44 of the groove.

With the ring supported on the base 40 of the groove with one facethereof in abutting intimate engagement,

with the wall 48 of the groove, compressive forces applied to theopposite face of the ring, particularly those having an axial component,will cause radial inward expansion of the ring effective to vary theposition of the sealing surface 36. Such compressive forces aremaintained on the ring by adjustable means, hereinafter described.

The adjustable means include a plurality of arcuate segments 62 adaptedto be disposed in the annular space between the valve seat ring 52 andthe wall 44 of the groove 40 in end-to-end relation and to be urged intopressure engagement with the valve seat ring 52. A plurality of chocks64 and shims 66 are also provided and are adapted to maintain thesegments in such pressure engagement.

More specifically, each segment 62 is in the form of an elongated barbowed slightly to render it arcuate when properly disposed in the groove38 and viewed in a plane normal to the flow axis of the passageway 16.The segments are preferably relatively short in length. For example,with segments approximately 4 inches in length, 12 segments are providedfor a valve having a flow passageway diameter of 16 inches. Each segmenthas one longitudinally extending wall contoured so as to enable it tointimately engage the adjacent face, i.e., the right hand face, of thevalve seat ring 52. Each segment is dimensioned so that when it is inintimate engagement with the ring, its lower surface 68 is elevatedslightly above the base 40 of the groove 38. Thus, the

segments 62 are readily movable axially within the annular space definedby the ring 52 and the groove wall 44.

The remaining longitudinally extending wall of each of the segments 62,i.e., the wall not in contact with the valve seat ring 52 (FIGS. 2 and3), is provided with a ledge 70 which slopes downwardly and to the leftas viewed in FIGS. 2 and 3, and with a face which extends from the leftedge of the ledge 70 to the left and in the direction of the flow axisof the valve body. The central portion 72 of this face is disposedgenerally parallel to the bearing surface 51 of the projection 50 and isbordered by upper and lower edges 74 and 76, respectively (FIG. 4),which lie in parallel planes normal to the flow axis of the fluid flowpassageway 16. On each side of the central portion 72 in the embodimentof FIG. 4 are a pair of flanking surfaces 78 which diverge away from thebearing face 51 of the projection. Adjacent each flanking surface 78 insuch embodiment is a second flanking surface 80 which is also inclinedrelative to the bearing surface 51 and which diverges at an even greaterangle from that surface. Adjacent each flanking surface 80 and locatedat each end of the segment is an end surface 82 which is generallyparallel to the bearing surface 51. This configuration of the segments62 facilitates positioning of the chocks 64 and shims 66, as will becomeapparent shortly.

In the embodiment of FIG. 5, the central portion 72 is of greaterlength, extending nearly to the end surfaces. 82 and connected theretoby an only slightly inclined surface 80. In both embodiments, thesurfaces 72 and 82 are parallel to one another, with the surface 72 incloser proximity to the bearing surface 51. In the embodiment of FIG. 5,ribs 83 are provided on the surface 72 in spaced relation to each endsurface 82 to facilitate positioning of two chocks. 64 and shims 66,relative to the surface 72.

A single chock 64 in the embodiment of FIG. 4, or two chocks in theembodiment of FIG. 5, and one or more shims 66 for each chock aretogether inserted intermediate each segment 62 and an adjacent portionof the bearing surface 51 of the projection 50. This may be done bylocating the chock 64 in engagement with the bearing surface 51 of theprojection 50 and placing one or more shims 66 intermediate the chockand segment, as in FIGS. 1 and 2, or may be done by placing the chock 64in engagement with the segment and placing one or more shims 66intermediate the chock and the bearing surface 51 as in FIGS. 3 and 4.

In either case, at least one chock 64 is provided for each segment 62and is adapted to be disposed adjacent the central portion 72 of thesegment, i.e., centrally of the segment in the embodiment'of FIG. 4 oradjacent each end of the central portion in the embodiment of FIG. 5.Each chock is generally of L-shapedcross section as viewed in a planecontaining the axis of the flow passageway 16 and includes a first leg84 having opposed parallel surfacesand a second leg 86 having convergingfaces. The outer surfaces of the chock, i.e., the surfaces adjacent theledge 70 and central portion 72 of the segment, are at the same angle toeach other as are the ledge 70 and central portion 72, while the innersurfaces of the chock are at the same angle to each other as the bearingsurface 51 and under surface of the projection 50. Thus, the chock canbe received snugly on the ledge of the segment or can snugly receive theprojection 50. Each chock is of limited width (FIG. 4), such width beingpreferably approximately the width of the central portion 72 of thesegment 62 in the embodiment of FIG. 4. In a preferred embodiment, thiswidth is one-fourth inch. In the embodiment of FIG. 2, the second leg 86of the chock is of such a length that its end wall 87 abuts the sidewall 44 of the valve body groove 38 so as to prevent premature tippingof the chock and, consequently, of the segment by forces which tend tomove the ring 52 out of the groove.

In the assembly of the butterfly valve 10, as illustrated in FIGS. 1-5,assuming all initial machining has been accomplished, the valve seat 52is inserted into the groove, 38 in abutting relation to the wall 46 ofthe groove and segments 62 are then placed in the groove in end-to-endrelation until they define a segmented ring. At this stage of assembly,an annular gap will exist intermediate the segments 62 and the oppositewall 44 of the groove, and the ring 52 will not be in axial compression.A chock 64 is then placed intermediate the segment 62 and the projection50 in the vicinity of the end surface 82 of the segment, there being aloose fit between the segment and projection at this point, because ofthe distance between the end surface 82 and the projection relative tothe size of the segment. A suitable tool such as a screwdriver is theninserted between the projection 50 and the segment in the vicinity ofthe central portion 72 to wedge the segment toward the valve seat ring52, thereby enlarging the gap between the segment and the wall 44 andplacing the ring 52 in compression. While the gap is so enlarged, thechock is moved along the segment until it is properly disposed relativeto the central portion 72. In the embodiment of FIG. 4, this isaccomplished by moving the chock past the inclined flanking surfaces 80and 78 until it is positioned generally centrally of the central portion72. In the embodiment of FIG. 5, this is accomplished by moving thechock directly from the surface 80 to the surface 72 until it ispositioned adjacent a rib 83. It will be noted that in the embodiment ofFIG. 5, two checks are employed, one adjacent each rib 83.

The foregoing operation is repeated for each segment until a chock ispositioned intermediate each central portion 72 and the adjacent bearingsurface 51 of the projection 50.

The proper or desirable degree of compression of the valve seat ring 52may be determined empirically by connecting the valve inlet to a sourceof fluid under pressure with the valve disc 28 in the closed positionand then checking the outlet side of the valve disc for leakage. Whenpoints of leakage are noted, shims 66 are placed either as shown in FIG.2 or as shown in FIG. 3 until the leakage is abated.

When theembodiment of FIG. 2 is employed, it is preferable that thecentral portion 72 of each segment be provided with a dimple 88 and thateach shim 66 be similarly dimpled, as at 90, the dimples being mutuallyalignable so that the shims are restrained from shifting movementrelative to one another and to the segment 62 when properly located. Thechock 64 may also be provided with an outwardly projecting teat to fitinto the dimples 90 of the shims. Alternatively, when the embodiment ofFIG. 3 is employed, i.e., when the chock 64 is nested on the ledge 70 ofthe segment 62, it is desirable to provide an indentation or dimple asat 92 in that face of the chock adjacent the bearing surface 51 of theprojection 50 and, again, to provide dimples 90 in the shims, therebyassuring a proper location of the shims relative to the chock. In theembodiment of FIG. 3, the position of each chock relative to itsadjacent segments may also be maintained by providing a notch 94 in thetop wall of the segment 62 and by prick punching the edge of the chockadjacent the notch to offset a small portion 96 of the edge of the chockoutwardly into the notch 94 to restrain the chock from lateral shiftingmovement relative to the segment.

With the construction thus provided, a plurality of segments defining aback-up ring for the resilient ring of the valve seat can be properlypositioned so as to maintain the resilient ring in a proper degree ofcompression and prevent leakage between the valve seat and ring.

While certain specific embodiments of the invention have been shown anddescribed, it should be apparent that various modifications may be madetherein without departing from the scope of the invention.

Various of the features of the invention are set forth in the followingclaims.

What is claimed is:

l. A butterfly valve comprising A. a valve body having a fluid flowpassageway provided with an inner annular groove defined by a baseencircling said passageway and opposed groove walls extending from saidbase in the direction of the flow axis of said passageway,

I. one of said groove walls being provided with a projection overhangingsaid groove base and extending in the direction of the other of saidgroove walls,

a. said projection defining aninclined bearing surface facing in thedirection of said groove base,

B. a ring defining a valve disc seat disposed in said annular groove andprojecting radially into said fluid flow passageway with one surface ofsaid ring in engagement with one of said opposed groove walls,

1. said ring being formed of a resilient material capable of expandingradially when subjected to forces having components extending in adirection parallel to the flow axis of said passageway,

2. said ring being proportioned so as to provide an annular spaceintermediate a portion of said ring and the other of said opposed groovewalls,

C. a plurality of segments disposed essentially endto-end in saidannular space for axially shifting movement,

1. one wall of each of said segments being contoured to conform to thatface of said ring opposite said one face,

2. the opposite wall of each of said segments being spaced from saidvalve body projection and defining a ledge and a face extending fromsaid ledge toward the flow axis of said valve body passageway, a. eachof said segment faces including a central portion disposed generallyparallel to said bearing surface of said projection and a flankingsurface having one end adjacent at least i one lateral edge of saidcentral portion,

1. the distance between the end of said flanking surface opposite saidone end and said bearing surface of said projection being significantlygreater than the distance between said central portion and said bearingsurface of said projection,

D. a chock for each of said segments having a length measuredcircumferentially of said valve body appreciably less than itsrespective segment and being adapted to be moved along said segment froma position between said flanking surface and said bearing surface ofsaid projection to a position between said central portion of saidsegment and the adjacent portion of the bearing surface of saidprojection,

1. said chock including a first surface adapted to be positionedadjacent and generally parallel to said central portion of said segment,a second surface adapted to be positioned adjacent and generallyparallel to said bearing surface of said projection, and a portionadapted to be positioned in underlying relation to the surface of saidprojection overhanging said groove base and in engagement with saidoverhanging surface,

a. said underlying portion being dimensioned so as to enable it to beeasily inserted beneath said projection when said chock is positionedadjacent said end of said flanking surface opposite said one end, 40

E. and shims disposed in contact with one of said first and secondsurfaces of said chock,

1. the distance between the first and second surfaces of said chock andthe thickness of said shims being determinative of the distance betweenthe central portion of said segment and said bearing surface of saidprojection and being determinative of the degree of compression of saidring.

2. A butterfly valve in accordance with claim 1, 5O

wherein said segments from essentially a continuous ring in said annularspace intermediate said seat defining ring and said other of saidopposed groove walls.

3. A butterfly valve in accordance with claim 1, wherein a divergingflanking surface is provided adjacent each of the lateral edges of saidcentral portion.

4. A butterfly valve inaccordance with claim 1, wherein said shims aredisposed intermediate said central portion of each of said segments andsaid first surface of said chock, and wherein said second surface ofsaid chock engages said bearing surface of said projection. i

5. A butterfly valve in accordance with claim 4,

wherein one of said central portion of said segment and said firstsurface of said chock is provided with an indentation, and wherein eachof said shims 1s indented to provide a dimple adapted to be receivedinto said first mentioned indentation and into the indentations of saidother shims to locate each of said shims in a predetermined position.

6. A butterfly valve in accordance with claim 1, wherein said shims aredisposed intermediate said bearing surface of said projection and saidsecond surface of said chock, and wherein said first surface of saidchock is in engagement with said central portion of said segment.

7. A butterfly valve in accordance with claim 6, wherein said secondsurface of'said chock is provided with an indentation, and wherein eachof said shims is indented to provide a dimple adapted to be receivedinto said indentation of said chock and into the indentations of saidother shims to locate said shims relative to said chock.

8. A butterfly valve in accordance with claim 6, wherein a groove isprovided on said segment to receive an offset portion of said chock tolocate said chock relative to said segment.

9. A butterfly valve in accordance with claim 1, wherein a pair of saidchocks is provided for each of said segments, said chocks are positionedadjacent each of opposite ends of said central portion of said segmentand in engagement therewith, and wherein means are provided to locatesaid chock relative to said central portion of said segment.

10. A butterfly valve in accordance with claim 1, wherein said portionof said chock underlying said projection includes a surface in abuttingengagement with said one of said groove walls underlying said projectionso as to resist tipping of said chock.

1. A butterfly valve comprising A. a valve body having a fluid flowpassageway provided with an inner annular groove defined by a baseencircling said passageway and opposed groove walls extending from saidbase in the direction of the flow axis of said passageway,
 1. one ofsaid groove walls being provided with a projection overhanging saidgroove base and extending in the direction of the other of said groovewalls, a. said projection defining an inclined bearing surface facing inthe direction of said groove base, B. a ring defining a valve disc seatdisposed in said annular groove and projecting radially into said fluidflow passageway with one surface of said ring in engagement with one ofsaid opposed groove walls,
 1. said ring being formed of a resilientmaterial capable of expanding radially when subjected to forces havingcomponents extending in A direction parallel to the flow axis of saidpassageway,
 2. said ring being proportioned so as to provide an annularspace intermediate a portion of said ring and the other of said opposedgroove walls, C. a plurality of segments disposed essentially end-to-endin said annular space for axially shifting movement,
 1. one wall of eachof said segments being contoured to conform to that face of said ringopposite said one face,
 2. the opposite wall of each of said segmentsbeing spaced from said valve body projection and defining a ledge and aface extending from said ledge toward the flow axis of said valve bodypassageway, a. each of said segment faces including a central portiondisposed generally parallel to said bearing surface of said projectionand a flanking surface having one end adjacent at least one lateral edgeof said central portion,
 1. the distance between the end of saidflanking surface opposite said one end and said bearing surface of saidprojection being significantly greater than the distance between saidcentral portion and said bearing surface of said projection, D. a chockfor each of said segments having a length measured circumferentially ofsaid valve body appreciably less than its respective segment and beingadapted to be moved along said segment from a position between saidflanking surface and said bearing surface of said projection to aposition between said central portion of said segment and the adjacentportion of the bearing surface of said projection,
 1. said chockincluding a first surface adapted to be positioned adjacent andgenerally parallel to said central portion of said segment, a secondsurface adapted to be positioned adjacent and generally parallel to saidbearing surface of said projection, and a portion adapted to bepositioned in underlying relation to the surface of said projectionoverhanging said groove base and in engagement with said overhangingsurface, a. said underlying portion being dimensioned so as to enable itto be easily inserted beneath said projection when said chock ispositioned adjacent said end of said flanking surface opposite said oneend, E. and shims disposed in contact with one of said first and secondsurfaces of said chock,
 1. the distance between the first and secondsurfaces of said chock and the thickness of said shims beingdeterminative of the distance between the central portion of saidsegment and said bearing surface of said projection and beingdeterminative of the degree of compression of said ring.
 2. A butterflyvalve in accordance with claim 1, wherein said segments from essentiallya continuous ring in said annular space intermediate said seat definingring and said other of said opposed groove walls.
 2. the opposite wallof each of said segments being spaced from said valve body projectionand defining a ledge and a face extending from said ledge toward theflow axis of said valve body passageway, a. each of said segment facesincluding a central portion disposed generally parallel to said bearingsurface of said projection and a flanking surface having one endadjacent at least one lateral edge of said central portion,
 2. said ringbeing proportioned so as to provide an annular space intermediate aportion of said ring and the other of said opposed groove walls, C. aplurality of segments disposed essentially end-to-end in said annularspace for axially shifting movement,
 3. A butterfly valve in accordancewith claim 1, wherein a diverging flanking surface is provided adjacenteach of the lateral edges of said central portion.
 4. A butterfly valvein accordance with claim 1, wherein said shims are disposed intermediatesaid central portion of each of said segments and said first surface ofsaid chock, and wherein said second surface of said chock engages saidbearing surface of said projection.
 5. A butterfly valve in accordancewith claim 4, wherein one of said central portion of said segment andsaid first surface of said chock is provided with an indentation, andwherein each of said shims is indented to provide a dimple adapted to bereceived into said first mentioned indentation and into the indentationsof said other shims to locate each of said shims in a predeterminedposition.
 6. A butterfly valve in accordance with claim 1, wherein saidshims are disposed intermediate said bearing surface of said projectionand said second surface of said chock, and wherein said first surface ofsaid chock is in engagement with said central portion of said segment.7. A butterfly valve in accordance with claim 6, wherein said secondsurface of Said chock is provided with an indentation, and wherein eachof said shims is indented to provide a dimple adapted to be receivedinto said indentation of said chock and into the indentations of saidother shims to locate said shims relative to said chock.
 8. A butterflyvalve in accordance with claim 6, wherein a groove is provided on saidsegment to receive an offset portion of said chock to locate said chockrelative to said segment.
 9. A butterfly valve in accordance with claim1, wherein a pair of said chocks is provided for each of said segments,said chocks are positioned adjacent each of opposite ends of saidcentral portion of said segment and in engagement therewith, and whereinmeans are provided to locate said chock relative to said central portionof said segment.
 10. A butterfly valve in accordance with claim 1,wherein said portion of said chock underlying said projection includes asurface in abutting engagement with said one of said groove wallsunderlying said projection so as to resist tipping of said chock.